Growth and reproductive properties of Tench, Tinca tinca Linnaeus, 1758 in Trasimeno Lake (Umbria, Italy)

Growth and some reproductive properties of native Tinca tinca Linnaeus, 1758 from Trasimeno Lake were investigated during 2009 and 2010. The total sample of fish (510) was composed by 126 males, 221 females and 163 immature specimens. Total length (TL ± 0.1 cm) and weight (W ± 0.1 g) were recorded; age estimation was based on scalimetry and sex was determined by microscopic observation of the gonads. Age composition varied from 1+ to 11+ . The TL-W relationship was log 10W = −2.235 + 3.248log 10TL. Previous growth was determined with back-calculation from scale measurements using the Fraser-Lee method. Theoretical length growth was estimated with von Bertalanffy’s model. Analysis of the gonadosomatic index (GSI) suggests that the reproductive period of the population took place from May to July. Sexual maturation occurred in both sexes at the second year of life. The mean diameter of eggs was 0.075 mm. The mean number of eggs produced by each female was 233 930 and increased with the size of the specimens. Though it is one of the most widespread and interested species in fishing in Italian waters, tench has not been widely studied; this research deepens some biological characteristics of this species that is strongly shrinking in Italy